Windowing

An amplitude weighting of the time signal used with gated continuous signals to give them a slow onset and cut-off in order to reduce the generation of side lobes in their frequency spectrum.

Transient analysis

• Uniform window - for general purposes.
• Force window - for short impulses and transients, to improve the signal to noise ratio.
• Exponential window - for transients longer than the record length, transients that do not decay sufficiently within the record length.

Continuous Signal Analysis

• Uniform window - should only be used when analysing special sinusoids, whose frequencies coincide with the centre frequencies in the analysis. This is often the situation when pseudo-random types of signal are analysed, or when order tracking is applied.
• Hanning window - is a general purpose window and should be used in most cases, because it has the best overall filter characteristic.
• Kaiser-Bessel and Blackman-Harris window - show very good selectivity and should be used for two-tone seperation of harmonic signals with widely different levels.
• Flattop window- is mainly desiigned for calibration and correct amplitude measurements.

Frequency Response Measurements

• Force window - for the excitation signal when an impact hammer is used for excitation.
• Exponential window - for the response signal of lightly damped systems, when an impact hammer is used for excitation.
• Hanning window - for both excitation and response signal when a random excitation signal is used.
• Uniform window - for both excitation and response signals when a pseudo-random excitation signal is used.

See also: Blackman Window, Blackman-Harris Window, Cauchy Window, Discrete Fourier Transform, Fast Fourier Transform, Flattop Window, Hamming Window, Hanning Window, Hanning-Poisson Window, Kaiser Bessel Window, Leakage.